The body has been found to have many time clocks – one governing the sleep-wake cycle in response to light and dark, and others in most of our body organs. These daily (circadian) rhythms are coordinated by the brain’s hypothalamus –which links the nervous system to the endocrine system via the pituitary gland. The pancreas secretes insulin during the day and slows down at night, meaning that blood sugar levels are better controlled in the morning than evening. The gut has a clock that controls nutrient absorption, and removal of waste. The microbiome –the trillions of bacteria in our digestive tract – also have a daily rhythm.
Dr. Satchin Panda of the Salk Institute is an expert on circadian rhythms research. He has just published a book on this subject – The Circadian Code - Lose Weight, Supercharge Your Energy and Transform Your Health from Morning to Midnight. He has studied genetically identical mice and divided them into two groups. One group could eat a diet of high fat, high sugar foods around the clock. The other group ate the same foods in a daily 8 hour window. Calories were similar for both groups. Those who ate around the clock became fat and sick, while those who ate in a time restricted fashion were protected from obesity, fatty liver and metabolic disease.
Courtney Peterson at the University of Alabama at Birmingham has also studied this subject and published several papers on her findings. She took a group of prediabetic men, and had them eat their meals in a 12 hour window for five weeks. In the next phase, these men were fed the same meals in a six hour window beginning each morning. They were eating enough calories to maintain their weight, to see whether time restricted eating had health benefits unrelated to weight loss. The men on the time restricted program had lower insulin, reduced levels of oxidative stress, less nighttime hunger, and significantly lower blood pressure – their systolic pressure dropped by roughly 11 points and their diastolic by 10 points. These are very significant results.
In other papers Dr. Peterson and colleagues have reviewed evidence that the circadian system plays a pervasive role in regulating glucose, insulin, lipid levels, appetite and energy metabolism in humans. Eating at the wrong times – late in the day – disrupts the circadian system and adversely affects metabolic health. Chronobiology is important in preventing and treating type 2 diabetes, obesity and high blood fats (hyperlipidemia).
The take home message from these findings is that eating early in the day will synchronize with your sleep-wake cycle and bring you many health benefits. If you are never hungry for breakfast, start by having a very small supper around 5 pm, and you will be hungrier in the morning. Have a healthy breakfast after waking, and aim for a 10 hour time for eating . As you get used to this new schedule, you can restrict your time further, depending on what results you are aiming for. You may worry that such a schedule will be a problem for your social life, and if you frequently meet friends for dinner and drinks in the evening, this is true. Perhaps you can socialize around lunch on the weekends, or break your schedule occasionally to be with friends, but eat lightly at dinner so you can return to your new way in the morning.
I suspect that the Marin County library system will purchase copies of Dr. Panda’s book – remember that they bought over 50 copies of Michael Pollan’s How to Change Your Mind. Stop by the library to find out.
Sadja Greenwood, MD, MPH
